And I'm Renee Montagne. Last night Texas executed Edgar Tamayo. There's no doubt about whether he committed the crime - it was 20 years ago in Houston that Tamayo, sitting in the back of a patrol car, pulled out a gun and shot a police officer in the head. There has been great cross-border controversy, however, about Tamayo's execution. He was Mexican and the Mexican government protested the death penalty up until his execution.

Even U.S. Secretary of State John Kerry weighed, in urging Texas Governor Rick Perry to stop it. Reaction to the execution has been strong in Mexico and we're joined by NPR's Carrie Kahn in Mexico City for more. Good morning.

CARRIE KAHN, BYLINE: Good morning, Renee.

MONTAGNE: Let's start with a little background. I've offered a few details. Give us some more.

KAHN: Sure. Edgar Tamayo was 46 years old and he grew up in a small town in the Mexican state of Morelos and that's south, here, of Mexico City. By all accounts he had a rough life here. His family was very poor and not very stable. He left Mexico when he was a teen for the U.S. to work and he entered illegally. He had several run-ins with the law for fights and robbery of a convenience store.

It was in January of 1994 when he was arrested following an incident in a Houston bar. Tamayo had been drinking. He was handcuffed and put in the squad car, as you said, by Houston police officer Guy Gaddis. So Tamayo was in the back of the car and apparently Gaddis had not found a gun that he had had hidden in his pants. And even though Tamayo was handcuffed he was able to pull out the gun and fire off six shots.

Three hit Gaddis in the back of the head and killed him. Tamayo was arrested a few blocks away, still handcuffed. Gaddis at the time left behind a wife who was pregnant.

MONTAGNE: So not a sympathetic character, if you will, but still again this execution has been controversial. But why? I mean, the U.S. has executed people from other countries before, including Mexicans nationals who have been executed in Texas. Why did Mexico object in this case in particular and why did Secretary of State Kerry get involved?

KAHN: So this case is one of many that's created tensions between the U.S. and Mexico. And the issue really stems from whether Tamayo and other Mexican nationals accused of a capital crime were advised of what's known as their consular rights. And that just means that any foreign national accused of a crime in the U.S. has the right to speak with somebody from their nation's consulate.

Tamayo was not informed of that right before trial and Mexico says they could've helped prepare his defense, possibly could've gotten his sentence commuted to life in prison instead of the death penalty. And Mexico actually took Tamayo's case and 50 others like it to the world court and they accused the U.S. of violating this international law. The court ordered the U.S. to review Tamayo's conviction and that of the other 50 Mexicans on Death Row in the United States. But that didn't happen.

MONTAGNE: Well, again, it's a big storey there in the Mexican press. Tell us what the headlines are.

KAHN: Sure. There's been quite a lot of press about the case and that's because there is no capital punishment in Mexico and really there are no life sentences, either. Prisoners, when they reach an old age, are usually released on humanitarian grounds. There are reports that he's been described as slightly mentally disabled - all issues that Mexican officials say were not properly considered by the U.S. jury when he was sentenced to death.

There have been some protests in his home state of Morelos. A group burned a U.S. flag last week and closed off a McDonald's and a Burger King. The Mexican ambassador in the U.S. said this issue over the Death Row inmates continues to be a significant irritant, is what he called it, in the two countries' relations. And Secretary of State Kerry warned that this case could affect the way Americans are treated abroad.

MONTAGNE: That would seem to be a concern.

KAHN: Definitely.

MONTAGNE: There are dozens more Mexican nationals on Death Row in the United States. Will this affect any of those?

KAHN: Well, we're going to be hearing more about these cases. There are still 48 Mexican nationals on Death Rows in the U.S. Tamayo was the third executed since that world court ruling that the U.S. violated the international law by not informing inmates of their rights to speak to a consular official. That ruling was in 2004 and then-president, George Bush, ordered Texas - he actually ordered Texas and the other states with Mexican nationals on Death Rows to review the case.

But the U.S. Supreme Court then stepped in and ruled, four years later, that the president didn't have the authority to order states to abide by a ruling of the international court. So we're bound to hear about more of these cases when these prisoners on Death Rows come up again for execution.

MONTAGNE: That's NPR's Carrie Kahn speaking to us from Mexico City on the execution last night of convicted murderer Edgar Tamayo. Carrie, thanks very much.